The present disclosure relates to a power feeding device, a power feeding method, and a power feeding system which charge an electronic device such as a mobile phone or the like in a contactless fashion.
In recent years, much attention has been paid to power feeding devices, referred to as contactless power feeding devices or wireless power feeding devices, which supply CE (Consumer Electronics) devices such as mobile phones, portable music players, etc. with electric power in a contactless fashion by way of electromagnetic induction, magnetic resonance, or the like. According to the contactless power feeding scheme, the connector of a power supply device such as an AC adapter does not need to be inserted into or connected to a CE device to charge the CE device. Rather, a CE device starts being charged simply when it is placed on a tray-type contactless power feeding device, which is also called a charging tray, for example. Consequently, no physical terminal connection is necessary between the CE device and the power feeding device.
Since a CE device starts being charged simply when it is placed on a charging tray, the user of the CE device is subject to a less burden in charging the CE device. One problem with the charging tray, however, is that an object other than the CE device to be charged, e.g., foreign matter such a coin or the like, hereinafter referred to as “foreign metal,” could easily be placed on the charging tray. When foreign metal is placed on the charging tray, the foreign metal tends to be heated by the charging tray.
There have been proposed various ways to detect foreign metal on a charging tray in order to stop the charging process of the charging tray if the foreign metal is placed on the charging tray. According to one proposal, for example, a temperature sensor is used to detect the temperature of an object which is placed on a charging tray, and the object is determined as being foreign matter if an abnormal temperature rise is detected (see, for example, Japanese Patent Laid-Open No. 2008-172874 (hereinafter referred to as Patent Document 1)). According to another proposal, a load on a charging tray is varied in a predetermine pattern to detect an overload (see, for example, Japanese Patent Laid-Open No. 2002-34169 (hereinafter referred to as Patent Document 1)).